Summary
The protein C pathway serves as a modulating system with both anti-inflammatory and
anticoagulant properties and is intimately involved in the pathophysiology of inflammation
and sepsis. Treatment with recombinant human activated protein C (rhAPC) can reduce
the mortality of severe sepsis. We investigated whether an elevation of plasma protein
C levels to supranormal levels by infusion of a protein C zymogen concentrate has
an effect on coagulation, protein C activation or inflammation in a human endotoxemia
model. Eleven healthy male volunteers were enrolled in a double-blind, placebo-controlled
two-way cross-over trial. Ten minutes after infusion of 2ng/kg endotoxin each volunteer
received either placebo or a plasmaderived protein C zymogen concentrate (Ceprotin®, Baxter) (150 U/kg as a slow bolus infusion followed by 30 U/kg/h continuous infusion
until 4 hours after LPS-infusion). Protein C antigen and activity increased 4– to
5-fold after infusion of the concentrate. APC was generated during endotoxin-induced
inflammation in the placebo (1.6 fold increase) and the protein C period (4.0-fold
increase).The increase of APC levels correlated with the TNF-α and IL-6 release in
both periods (r=0.65–0.68; p<0.05) and paralleled the protein C antigen and activity
levels in the period with supranormal protein C levels. Supra normal protein C levels
resulted in slightly, although non-significant, lower tissue factor mRNA expression
and thrombin generation (TAT, F1+2). Systemic inflammation (TNF-α, IL-6) was not influenced
by protein C zymogen concentrate administration. Infusion of protein C zymogen was
safe and no adverse effects occurred. The increase of protein C levels several fold
above the normal range resulted in a proportional increase of the APC levels, but
had no major anticoagulant, anti-inflammatory or profibrinolytic effects. Low grade
endotoxemia itself induces significant protein C activation, which correlates with
the TNF release.
Keywords
Endotoxin - protein C - coagulation - inflammation